1. Field of The Invention
The present invention relates to an acyl group-containing hexaazaisowurtzitane derivative, and a method for producing the same.
The acyl group-containing hexaazaisowurtzitane derivative of the present invention contains an Nxe2x80x94A group (wherein A represents an acyl group) and optionally an Nxe2x80x94H group in high concentration, wherein each of the Nxe2x80x94A group and the Nxe2x80x94H group can be converted to an Nxe2x80x94NO2 group by various nitration methods.
Therefore, the acyl group-containing hexaazaisowurtzitane derivative of the present invention is useful as a precursor of a polynitrohexaazaisowurtzitane derivative which can be used not only as a material for explosives but also as an additive for propellants and explosives. More specifically, a polynitrohexaazaisowurtzitane derivative can be advantageously used as an additive for improving various properties (such as mechanical properties, detonation velocity, detonation pressure, burning rate, pressure exponent, sensitivity, and heat resistance) of propellants and explosives. In addition, hexanitrohexaazaisowurtzitane (hereinafter referred to simply as xe2x80x9cHNWxe2x80x9d), which is a typical example of the polynitrohexaazaisowurzitan derivative, has been expected to be a promising material for the next-generation high performance explosives. As mentioned above, the acyl group-containing hexaazaisowurtzitane derivative of the present invention is useful as a precursor of such a valuable polynitrohexaazaisowurzitane derivative.
Further, the acyl group-containing hexaazaisowurtzitane derivative of the present invention can be advantageously used, by virtue of the reactivity of each of the Nxe2x80x94A group (wherein A represents an acyl group) and the Nxe2x80x94H group which are contained therein, for producing a highly polar polymer containing acyl groups in the main and/or side chain thereof in high concentration. This highly polar polymer is useful not only as a highly hydrophilic polymer but also as a highly dielectric polymer.
Still further, the acyl group-containing hexaazaisowurtzitane derivative of the present invention can be advantageously used as a polyfunctional crosslinking agent by virtue of the reactivity of the derivative.
Furthermore, the acyl group-containing hexaazaisowurtzitane derivative of the present invention can also be used as various types of additives, such as a polymer modifier and the like.
2. Prior Art
In addition to the above-mentioned HNW, conventionally known compounds, which have the same hexaazaisowurtzitane (hereinafter referred to simply as xe2x80x9cWxe2x80x9d) skeleton as in the acyl group-containing hexaazaisowurtzitane derivative of the present invention, include the following:
(1) hexakis(arylmethyl)hexaazaisowurtzitane (hereinafter referred to simply as xe2x80x9cHBWxe2x80x9d);
(2) tetraacetyldibenzylhexaazaisowurtzitane (hereinafter referred to simply as xe2x80x9cTADBWxe2x80x9d); and
(3) hexaazaisowurtzitane having a trimethylsilyl-ethyloxycarbonyl group (hereinafter referred to simply as xe2x80x9cHCWxe2x80x9d) (see Unexamined Japanese Patent Application Laid-Open Specification No. 6-321962).
It is known that HBW can be obtained by a condensation reaction of various arylmethylamines with glyoxal [see J. Org. Chem., vol. 55, 1459-1466 (1990)].
It has been reported that TADBW is useful as a material for producing explosives [see The Militarily Critical Technologies List, Office of the Under Secretary of Defense for Acquisition, 12-22, October (1992)]. However, this reference neither describes a method for converting TADBW to an explosive, the chemical structure of such an explosive obtained from TADBW nor a method for producing TADBW itself.
The properties of HNW, which has been expected to be a promising material for high performance explosives as mentioned above, are described in International Symposium on Energetic Materials Technology, PROCEEDINGS, SEPTEMBER 24-27, 76-81 (1995): COMBUSTION AND FLAME 87, 145-151 (1991) and the like, but a method for producing HNW has not been reported in any literature.
Previously, with a view toward developing a method for producing a polynitrohexaazaisowurtzitane derivative, such as HNW, the present inventors tried to nitrate HBW and TADBW under various nitration conditions. However, it was impossible to obtain a satisfactory amount of a polynitrohexaazaisowurtzitane derivative. Further, HBW and TADBW have a benzyl group, so that, when HBW or TADBW is subjected to nitration, nitroaromatic compounds having high affinity for various nitro compounds are inevitably produced as a by-product. As a result, it is difficult to separate the desired polynitrohexaazaisowurtzitane derivative from the by-produced nitroaromatic compounds.
It is also difficult to obtain HCW in high yields. The reason for this is considered to reside in that, during the production of HCW, hydrochloric acid (which is a strong acid) is generated, and the generated hydrochloric acid is likely to decompose HBW as a starting material.
Thus, all of the W skeleton-containing compounds of HBW, TADBW and HCW are not suitable as precursors which can be advantageously used for producing a polynitrohexaazaisowurtzitane derivative, such as HNW or the like, on a commercial scale.
In these situations, with a view toward developing a commercially advantageous method for producing a polynitrohexaazaisowurtzitane derivative, the present inventors have made extensive and intensive studies in order to find not only a precursor which can be easily converted to a polynitrohexaazaisowurtzitane derivative, but also a method for producing the precursor.
As a result, it has unexpectedly been found that a hexaazaisowurtzitane derivative having a polar group moiety comprised only of an N-acyl group and optionally an Nxe2x80x94H group is useful as a precursor of a polynitrohexaazaisowurtzitane derivative. The present inventors have also found a commercially advantageous method for producing the above-mentioned hexaazaisowurtzitane derivative in high yield. It has further been found that a hexaazaisowurtzitane derivative having an N-acyl group, an N-alkyl group and optionally an Nxe2x80x94H group can be advantageously used as a polyfunctional crosslinking agent. The present invention has been completed based on these novel findings.
It is an object of the present invention to provide the above-mentioned hexaazaisowurtzitane derivative, and it is another object of the present invention to provide a method for producing the same.
It is a further object of the present invention to provide a novel functional material which contains a highly polar, functional group, such as an N-acyl group and an Nxe2x80x94H group, in high concentration.
In one aspect of the present invention, there is provided an acyl group-containing hexaazaisowurtzitane derivative represented by the following formula (I):
WAtQ(6xe2x88x92t)xe2x80x83xe2x80x83(I)
wherein t represents an integer of from 4 to 6, each A independently represents an acyl group having 1 to 10 carbon atoms, each Q independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and W represents a hexavalent hexaazaisowurtzitane residue represented by the following formula (II): 
In another aspect of the present invention, there is provided a method for producing the above-mentioned acyl group-containing hexaazaisowurtzitane derivative.
Hereinbelow, explanation is made with respect to an acyl group-containing hexaazaisowurtzitane derivative represented by formula (I-a) below, as a typical example of the compound of formula (I) above.
WAtH(6xe2x88x92t)xe2x80x83xe2x80x83(I-a)
wherein t represents an integer of from 4 to 6, A represents an acyl group having 1 to 10 carbon atoms, H represents a hydrogen atom, and W represents a hexavalent hexaazaisowurtzitane residue represented by the following formula (II): 
With respect to the acyl group A in the hexaazaisowurtzitane derivative of the present invention, there is no particular limitation as long as it has 1 to 10 carbon atoms. The acyl group may be substituted with a substituent which is stable under reaction conditions for a reductive dearylmethylation reaction conducted in the method of the present invention as described below. Examples of acyl groups include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, a hexanoyl group and a 2-phenylacetyl group. Of these, acyl groups having 2 to 5 carbon atoms, such as an acetyl group, a propionyl group, a butyryl group and a valeryl group, are preferred. Acyl groups having 2 to 3 carbon atoms, such as an acetyl group and a propionyl group, are more preferred. The acyl groups represented by At in formula (I-a) above may be the same or different.
With respect to the acyl group-containing hexaazaisowurtzitane derivative of the present invention represented by formula (I-a): WAtH(6xe2x88x92t), a plurality of types of isomers are present which have the same value for t but are different in regard to the positions of N-acyl groups and Nxe2x80x94H groups.
For example, as a representative example of compounds represented by formula (I-a) WAtH(6xe2x88x92t) wherein t is 4, i.e., compounds represented by the formula WA4H2, a compound represented by the formula (I-axe2x80x2) below can be mentioned, but the compound represented by formula WA4H2 may be any of the structural isomers of the compound of formula (I-axe2x80x2) below: 
In the acyl group-containing hexaazaisowurtzitane derivative WAtH(6xe2x88x92t) of the present invention, t represents an integer of from 4 to 6, preferably 4 or 6.
One preferred example of the acyl group-containing hexaazaisowurtzitane derivative of the present invention is a compound represented by formula (I-a) wherein t is 6, that is, a hexaacylhexaazaisowurtzitane represented by the following formula (III):
WA6xe2x80x83xe2x80x83(III)
wherein A represents an acyl group having 1 to 10 carbon atoms, and W represents a hexavalent hexaazaisowurtzitane residue.
The hexaacylhexaazaisowurtzitane of formula (III) above is advantageous in that, since the structure of the compound is simple, the compound can be easily obtained in a highly purified form. In this connection, it should further be noted that, among compounds of formula (III), a hexaacetyl compound can be purified by sublimation, so that a highly purified WA6 (A: acetyl group) can be easily obtained from a reaction mixture.
Another preferred example of an acyl group-containing hexaazaisowurtzitane derivative of the present invention is a compound represented by formula (I-a) wherein t is 4. This compound is advantageous in that since Nxe2x80x94H groups contained therein have high reactivity, it is possible for the Nxe2x80x94H groups to be selectively reacted. For example, by selectively nitrating the Nxe2x80x94H groups, a dinitrohexaazaisowurtzitane derivative can be easily obtained in high yield.
As mentioned above, the acyl group-containing hexaazaisowurtzitane derivative of the present invention contains an Nxe2x80x94A group (wherein A represents an acyl group) and optionally an Nxe2x80x94H group in high concentration, wherein each of the Nxe2x80x94A group and the Nxe2x80x94H group can be converted to an Nxe2x80x94NO2 group by various nitration methods.
The following examples describe methods for producing the acyl group-containing hexaazaisowurtzitane derivative of formula (I-a).
The hexaacylhexaazaisowurtzitane WA6, which is a preferred example of the acyl group-containing hexaazaisowurtzitane derivative of the present invention, can be obtained by acylating the acyl group-containing hexaazaisowurtzitane derivative WAnH(6xe2x88x92n) (wherein n is 4 or 5) with an acylating agent as shown in the following formula (1): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, H represents a hydrogen atom, and W represents a hexavalent hexaazaisowurtzitane residue.
The WAnH(6xe2x88x92n) (wherein n is 4 or 5) used in the reaction of formula (1) above is not disclosed in any prior art literature, and has for the first time been synthesized by the present inventors. The method for producing the WAnH(6xe2x88x92n) first requires the following explanation of the method for producing WA6.
With respect to the acylating agent used in the reaction of formula (1), there is no particular limitation as long as it is capable of acylating a secondary amino group contained in the WAnH(6xe2x88x92n) (wherein n is 4 or 5). Examples of acylating agents include acyl halides, such as acetyl chloride, acetyl bromide and propionyl chloride; carboxylic esters of N-hydroxysuccinimide, such as N-acetoxysuccinimide, N-propionyloxysuccinimide and N-(2-phenylacetoxy)succinimide; carboxylic anhydrides, such as acetic anhydride, propionic anhydride, lactic anhydride and an anhydride of a mixture of acetic and formic acid; and acylimidazoles, such as acetylimidazole and propionylimidazole. Among the above-mentioned acylating agents, acyl halides (such as acetyl chloride, propionyl chloride and the like) are preferred.
With respect to a reaction solvent to be used in the reaction of formula (1), there is no particular limitation as long as the solvent is capable of dissolving the WAnH(6xe2x88x92n) (wherein n is 4 or 5) and the solvent does not adversely affect the reaction. Examples of solvents include carboxylic acids, such as acetic acid, propionic acid and lactic acid; aprotic polar solvents, such as dimethyl sulfoxide and dimethylacetamide; and carboxylic anhydrides, such as acetic anhydride and propionic anhydride. Of these, carboxylic anhydrides (such as acetic anhydride, propionic anhydride and the like) are preferred. The above-mentioned solvents can be used individually or in combination.
The reaction temperature for the reaction of formula (1) is generally in the range of from xe2x88x9210 to 300xc2x0 C., preferably from 0 to 150xc2x0 C.
The WA6 obtained by the reaction of formula (1) can be isolated by a conventional method. For example, the isolation of the WA6 can be conducted by distilling off the solvent from the reaction mixture after completion of the reaction (see, for example, Example 1). Also, the purification of the WA6 can be conducted by a conventional method. Examples of methods for the purification include a method in which the isolated WA6 is subjected to sublimation at 270xc2x0 C. under reduced pressure of 10 mmHg (see, for example, Example 1); a method in which the isolated WA6 is recrystallized from toluene (see, for example, Example 2); and a method in which the isolated WA6 is reprecipitated from chloroform.
The WA6 of the present invention can also be obtained by subjecting an acyl group- and arylmethyl group-containing hexaazaisowurtzitane derivative represented by the formula WAnB(6xe2x88x92n) to reductive dearylmethylation and then, acylating the resultant with an acylating agent, as shown in the following formula (2): 
wherein n represents an integer of from 4 to 5; A represents an acyl group having 1 to 10 carbon atoms; B represents an arylmethyl group represented by formula (XIII) described below; H represents a hydrogen atom; and W represents a hexavalent hexaazaisowurtzitane residue.
The WAnB(6xe2x88x92n) as the starting material in the reaction of formula (2) above has no particular limitation on the source or method of production thereof.
For example, WAnB(6xe2x88x92n) which is produced from a hexakis(arylmethyl)hexaazaisowurtzitane (WB6) by a method as described below or which is commercially available can be used without any restriction.
In the above-mentioned process of formula (2), the reductive dearylmethylation (step a) can be performed according to any of conventional methods, as long as it is capable of advancing the reductive dearylmethylation reaction of the WAnB(6xe2x88x92n). Generally, the reductive dearylmethylation (step a) is performed by contacting the WAnB(6xe2x88x92n) with a reduction catalyst in the presence of a reducing agent.
As the reducing agent, hydrogen gas, hydrazine, formic acid or the like is generally used, and hydrogen gas is preferably used. As the reduction catalyst, a catalyst containing a metal belonging to the platinum family or containing a derivative thereof, is generally used. Preferred examples of reduction catalysts include Pd compounds [such as Pd(OAc)2, PdCl2, Pd(NO3)2, PdO, Pd(OH)2, Pd3Pb1 and Pd3Te1], Pd alloys and metallic Pd; and Ru compounds (such as RuCl3), Ru alloys and metallic Ru. Of these, Pd compounds [such as Pd(OAc)2, PdCl2 and the like], Pd alloys and metallic Pd are more preferred. These reduction catalysts as such can be used. Alternatively, these reduction catalysts can be used in such a form as carried on various types of carriers, such as activated carbon, silica, alumina, silica-alumina, zeolite and activated clay. The catalyst may be subjected to reduction treatment prior to use in the above-mentioned reductive dearylmethylation reaction. In the case of a catalyst carried on a carrier, the acidity of the surface of the carrier can be controlled by inactivating acid sites present on the surface of the carrier by silylation, acylation or the like, or treating the carrier so that an alkaline substance (e.g., NaOH) is adsorbed on the surface of the carrier. The amount of the reduction catalyst varies depending on the reducing activity of the catalyst. However, the catalyst is used generally in an amount of from 0.0001 to 10, preferably from 0.001 to 1, in terms of the weight ratio of the metal of the catalyst to the WAnB(6xe2x88x92n).
With respect to a reaction solvent to be used in the reductive dearylmethylation (step a) of the process of formula (2) above, there is no particular limitation as long as the solvent is capable of dissolving the WAnB(6xe2x88x92n) and the solvent does not adversely affect the reaction. Examples of solvents include carboxylic acids, such as acetic acid, propionic acid and lactic acid; amide compounds, such as dimethylacetoamide; and amine compounds, such as N,N-dimethylaniline. The above-mentioned solvents can be used individually or in combination. From the viewpoint of achieving a high reaction rate, it is preferred to use a carboxyilic acid (such as acetic acid, propionic acid or the like) as the solvent.
The amount of the solvent varies depending on the dissolving capability of the solvent and the reaction temperature. The solvent is used generally in an amount of from 1 to 500, preferably from 5 to 100, in terms of the weight ratio of the solvent to the WAnB(6xe2x88x92n).
The reaction pressure for the reductive dearylmethylation (step a) of the process of formula (2) is generally in the range of from 0.1 to 1,000 kgf/cm2, preferably from 1 to 100 kgf/cm2. When hydrogen gas is used as a reducing agent, the reaction pressure is preferably in the range of from 0.1 to 500 kgf/cm2, more preferably from 1 to 100 kgf/cm2, in terms of hydrogen partial pressure. In addition to the hydrogen gas, inert gases, such as nitrogen, argon and helium gases, may be present in the reaction system.
The reaction temperature for the reductive dearylmethylation (step a) of the process of formula (2) is generally in the range of from xe2x88x9220 to 300xc2x0 C., preferably from 0 to 200xc2x0 C.
The reaction time for the reductive dearylmethylation (step a) of the process of formula (2) varies depending on the types of the catalyst, solvent, and the like. The reaction time is generally in the range of from 0.1 to 500 hours, preferably from 1 to 200 hours.
By the reductive dearylmethylation reaction (step a) of the process of formula (2), a WAnH(6xe2x88x92n) (wherein n is 4 or 5) is synthesized. Then, the synthesized WAnH(6xe2x88x92n) is subjected to acylation (step b) of the process of formula (2).
With respect to the acylating agent, solvent and reaction conditions (such as reaction temperature and the like) employed in the acylation (step b) of the process of formula (2), those which are mentioned in connection with the acylation reaction of formula (1) above can be employed.
The isolation and the purification of the obtained WA6 can be conducted by the method mentioned in connection with the reaction of formula (1) above.
The WA6 which is one example of the acyl group-containing hexaazaisowurtzitane derivative of the present invention can also be obtained by subjecting WB6 to reductive dearylmethylation in the presence of an acylating agent to obtain a first reaction product and then, subjecting the first reaction product to reductive dearylmethylation in the absence of an acylating agent to obtain a second reaction product and then subjecting the second reaction product to acylation, as shown in the following formula (3): 
wherein n represents an integer of from 4 to 5; A represents an acyl group having 1 to 10 carbon atoms; B represents an arylmethyl group; and W represents a hexavalent hexaazaisowurtzitane residue.
The reductive dearylmethylation in the presence of an acylating agent in step a of the process of formula (3) above is generally performed by contacting WB6 with a reduction catalyst in the presence of an acylating agent and a reducing agent. With respect to the reducing agent and the catalyst, there is no particular limitation as long as they can advance the reductive dearylmethylation reaction of the WB6 and do not deactivate the acylating agent in the reaction system. As the reducing agent, hydrogen gas, formic acid or the like is generally used, and hydrogen gas is preferably used. As the reduction catalyst, those which are mentioned in connection with the reductive dearylmethylation (step a) of the process of formula (2) above can be employed.
The amount of the catalyst varies depending on the reducing activity of the catalyst. The reduction catalyst is used generally in an amount of from 0.0001 to 20, preferably from 0.001 to 10, in terms of the weight ratio of the metal of the catalyst to the WB6.
With respect to the acylating agent to be used in the reductive dearylmethylation in the presence of an acylating agent in step a of the process of formula (3), there is no particular limitation as long as it is capable of acylating a secondary amino group which is formed by the reductive dearylmethylation of the WB6. Examples of acylating agents include carboxylic esters of N-hydroxysuccinimide, such as N-acetoxysuccinimide, N-propionyloxysuccinimide and N-(2-phenylacetoxy)succinimide; carboxylic anhydrides, such as acetic anhydride, propionic anhydride, lactic anhydride and an anhydride of a mixture of acetic and formic acid; and acylimidazoles, such as acetylimidazole and propionylimidazole. Among these acylating agents, carboxylic esters of N-hydroxysuccinimide (such as N-acetoxysuccinimide, N-propionyloxysuccinimide and the like) are preferred because the selectivity for a WAnB(6xe2x88x92n) (wherein n is 4 or 5) is improved. These acylating agents can be used individually or in combination. Especially, a mixture of a carboxylic ester of N-hydroxysuccinimide (such as N-acetoxysuccinimide, N-propionyloxysuccinimide or the like) and a carboxylic anhydride (such as acetic anhydride, propionic anhydride or the like) is preferred as the acylating agent, because not only does the reaction rate of the reductive dearylmethylation in step a of the process of formula (3) become high, but the selectivity for a WAnB(6xe2x88x92n) (wherein n is 4 or 5) is also improved.
The amount of the acylating agent varies depending on the reactivity of the acylating agent, the reaction mode and the reaction conditions. The acylating agent is used generally in an amount of from 0.1 to 100, preferably from 1 to 50, in terms of the molar ratio of the acylating agent to the arylmethyl groups of the WB6. When the mixture of a carboxylic ester of N-hydroxysuccinimide and a carboxylic anhydride is used as the acylating agent, the amount of the carboxylic anhydride is generally in the range of from 0.01 to 100, preferably from 0.1 to 10, in terms of the molar ratio of the carboxylic anhydride to the carboxylic ester of N-hydroxysuccinimide.
With respect to a reaction solvent to be used in the reductive dearylmethylation in the presence of an acylating agent in step a of the process of formula (3), there is no particular limitation as long as the solvent is capable of dissolving the WB6 and the solvent does not adversely affect the reaction. Examples of solvents include aromatic compounds, such as benzene, toluene, ethylbenzene, xylene, cumene, cymene, diisopropylbenzene and phenyl ethyl ether; cyclic, linear or branched ethers, such as tetrahydrofuran, dioxane, tetrahydropyran, diethyl ether, dipropyl ether and diisopropyl ether; and aliphatic alcohols, such as methanol, ethanol, propanol, isopropyl alcohol and t-butyl alcohol. These solvents can be used individually or in combination. Among the above-mentioned solvents, aromatic compounds (such as benzene, toluene, ethylbenzene, xylene and the like) are preferred because the reaction rate of the reductive dearylmethylation reaction of the WB6 increases with these solvents.
The amount of the solvent varies depending on the dissolving capability of the solvent and the reaction temperature. The solvent is used generally in an amount of from 0.1 to 100, preferably from 1 to 100, in terms of the weight ratio of the solvent to the WB6.
The reaction pressure for the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (3) is generally in the range of from 0.1 to 1,000 kgf/cm2, preferably from 1 to 300 kgf/cm2. When hydrogen gas is used as the reducing agent, in some cases, the reaction rate is increased in accordance with the increase of the reaction pressure. The reaction pressure is preferably in the range of from 0.1 to 500 kgf/cm2, more preferably from 1 to 200 kgf/cm2, in terms of the hydrogen partial pressure. In addition to the hydrogen gas, inert gases, such as nitrogen, argon and helium gases, may be present in the reaction system.
The reaction temperature for the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (3) is generally in the range of from xe2x88x9220 to 300xc2x0 C., preferably from 0 to 200xc2x0 C.
In the process of formula (3), the reductive dearylmethylation reaction (step a) is terminated when the WAnB(6xe2x88x92n) has been formed in a substantial amount. Specifically, the advance of the dearylmethylation reaction is monitored by gas chromatography or liquid chromatography, and the reaction is terminated when the WAnB(6xe2x88x92n) has been formed in a desired amount.
The reaction time varies depending on the types of the catalyst, acylating agent, solvent, and the like. The reaction time is generally in the range of from 0.1 to 500 hours, preferably from 1 to 200 hours.
By the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (3), a WAnB(6xe2x88x92n) (wherein n is 4 or 5) is synthesized. Then, the synthesized WAnB(6xe2x88x92n) is subjected to reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (3).
With respect to the catalyst, reducing agent, solvent, and reaction conditions (reaction temperature, reaction pressure, and the like) to be employed in the reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (3), those which are mentioned in connection with the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (3) above can be employed. Alternatively, the catalyst, reducing agent, solvent and reaction conditons which are mentioned in connection with the reductive dearylmethylation in step a of the process of formula (2) above can be employed.
From the reaction mixture obtained by the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (3), the acylating agent is removed, and the resultant acylating agent-removed mixture is subjected to reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (3). In this instance, it is preferred not to remove the reduction catalyst and solvent used in the reductive dearylmethylation in step a, but to leave it in the reaction mixture obtained by the reductive dearylmethylation in step a and use it in situ in the next reductive dearylmethylation in step b.
Reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (3) synthesizes a WAnH(6xe2x88x92n) (wherein n is 4 or 5) which is then subjected to acylation in step c of the process of formula (3).
With respect to the acylating agent, solvent and reaction conditions (reaction temperature, and the like) to be employed in the acylation in step c of the process of formula (3), those which are mentioned in connection with the acylation reaction of formula (1) above can be employed.
The reaction mixture obtained by the reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (3) above can be subjected to in situ acylation with an acylating agent in step c of the process of formula (3). Alternatively, the reaction mixture obtained by the reductive dearylmethylation in step b can be subjected to acylation in step c after the reduction catalyst and/or the solvent has been removed from the reaction mixture.
The isolation and the purification of the obtained WA6 can be conducted by the method mentioned in connection with the reaction of formula (1) above.
The WA6 can also be obtained by subjecting a WAnB(6xe2x88x92n) to reductive dearylmethylation in the presence of an acylating agent, as shown by the following formula (4): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, and W represents a hexavalent hexaazaisowurtzitane residue.
With respect to the reducing agent, reduction catalyst, acylating agent, solvent, reaction conditions (e.g., reaction temperature, reaction pressure, and the like), those which are mentioned in connection with the reaction of formula (9) (infra) can be used.
The WA6 can also be obtained by subjecting a WB6 to reductive dearylmethylation in the presence of an acylating agent, as shown by the following formula (5): 
wherein B represents an arylmethyl group, A represents an acyl group having 1 to 10 carbon atoms, and W represents a hexavalent hexaazaisowurtzitane residue.
With respect to the reducing agent, reduction catalyst, acylating agent, solvent, reaction conditions and the like to be employed in the reaction of formula (5) above, those which are mentioned in connection with step a of the process of formula (3) above can be employed.
The isolation and the purification of the obtained WA6 can be conducted by the method mentioned in connection with the reaction of formula (1) above.
As another example of the acyl group-containing hexaazaisowurtzitane derivative of the present invention, a compound represented by the formula WAnH(6xe2x88x92n) (wherein n is 4 or 5) can be mentioned, which can be obtained by subjecting a WAnB(6xe2x88x92n) (wherein n is 4 or 5) to reductive dearylmethylation in the absence of an acylating agent, as shown in the following formula (6): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, and W represents a hexavalent hexaazaisowurtzitane residue.
With respect to the reducing agent, reduction catalyst, solvent, reaction conditions and the like to be employed in the reaction of formula (6) above, those which are mentioned in connection with step a of the process of formula (2) above can be employed.
The WAnH(6xe2x88x92n) obtained by the reaction of formula (6) can be isolated by a conventional method. For example, the isolation can be conducted by a method comprising: removing the catalyst by filtration from the reaction mixture after completion of the reductive dearylmethylation reaction, thereby obtaining a filtrate; and distilling off the solvent from the obtained filtrate (see, for example, Example 5).
The acyl group-containing hexaazaisowurtzitane derivative WAnH(6xe2x88x92n) (wherein n is 4 or 5) of the present invention can also be obtained by a) subjecting WB6 to reductive dearylmethylation in the presence of an acylating agent and then, b) subjecting the resultant to reductive dearylmethylation in the absence of an acylating agent, as shown in the following formula (7): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, H represents a hydrogen atom, and W represents a hexavalent hexaazaisowurtzitane residue.
With respect to the reducing agent, reduction catalyst, acylating agent, solvent, reaction conditions and the like to be employed in the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (7) above, those which are mentioned in connection with step a of the process of formula (3) above can be employed.
By the reductive dearylmethylation (in the presence of an acylating agent) in step a of the process of formula (7), a WAnB(6xe2x88x92n) (wherein n is 4 or 5) is synthesized, and the synthesized WAnB(6xe2x88x92n) is subjected to reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (7).
With respect to the reducing agent, reduction catalyst, solvent, reaction conditions and the like to be employed in the reductive dearylmethylation (in the absence of an acylating agent) in step b of the process of formula (7), those which are mentioned in connection with step b of the process of formula (3) above can be used.
The isolation of the obtained WAnH(6xe2x88x92n) can be conducted by the method mentioned in connection with the reaction of formula (6) above.
The WAnB(6xe2x88x92n), which is a starting material for synthesizing the acyl group-containing hexaazaisowurtzitane derivative WAnH(6xe2x88x92n) of the present invention, can be obtained by subjecting a WB6 to reductive dearylmethylation in the presence of an acylating agent, as shown in the following formula (8): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, and W represents a hexavalent hexaazaisowurtzitane residue.
With respect to the reducing agent, reduction catalyst, acylating agent, solvent, reaction conditions and the like to be employed in the reaction of formula (8) above, those which are mentioned in connection with step a of the process of formula (3) above can be employed.
The WAnB(nxe2x88x926) obtained by the reaction of formula (8) can be isolated by a conventional method. For example, the isolation can be conducted by a method comprising: subjecting the reaction mixture obtained by the reductive dearylmethylation to filtration using a filter paper to filter off a precipitate and the catalyst; treating the precipitate on the filter paper with chloroform to dissolve the precipitate therein; distilling off the solvent and chloroform from the filtrate to obtain a solid residue; dissolving the solid residue in chloroform to obtain a solution; adding an aqueous ammonia solution to the obtained solution; separating the resultant mixture into an aqueous phase and a chloroform phase; isolating the chloroform phase; and distilling off the solvent from the chloroform phase (see, for example, Example 19).
In the above-mentioned reductive dearylmethylation reaction in the presence of an acylating agent, a side reaction occurs in which an N-acyl group formed by the main reaction is further reduced to an N-alkyl group.
Thus, as mentioned above, according to the present invention, there is also provided an N-alkyl group-containing hexaazaisowurtzitane derivative represented by the following formula (XII):
WAnQ(6xe2x88x92n)xe2x80x83xe2x80x83(XII)
wherein n represents an integer of from 4 to 5, each A independently represents an acyl group having 1 to 10 carbon atoms, each Q independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms provided that all of Q""s are not simultaneously hydrogen atoms, and W represents a hexavalent hexaazaisowurtzitane residue represented by the following formula (II): 
As mentioned above, the N-alkyl group-containing hexaazaisowurtzitane derivative can be advantageously used as a polyfunctional crosslinking agent.
Examples of N-alkyl group-containing hexaazaisowurtzitanes include diethyltetraacetylhexaazaisowurtzitane (WA4R2) obtained in Examples 6-12, ethylpentaacetylhexaazaisowurtzitane (WA5R1) obtained in Examples 13 and 14, and monoalkyltetraacetylhexaazaisowurtzitane (WA4RH) shown in Chart [formula (12)].
The N-alkyl group-containing hexaazaisowurtzitane derivative can be obtained by subjecting a WAnB(6xe2x88x92n) to reductive dearylmethylation in the presence of an acylating agent, as shown in the following formula (9): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, each Q independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms provided that all of Q""s are not simultaneously hydrogen atoms, and W represents a hexavalent hexaazaisowurtzitane residue.
The reductive dearylmethylation reaction of formula (9) above can be effected under substantially the same conditions as mentioned in connection with the reductive dearylmethylation reaction in step a of the process of formula (2) above, except that the reaction of formula (9) is conducted in the presence of an acylating agent.
In the reductive dearylmethylation reaction (in the presence of an acylating agent) of formula (9), the acylating agents which are mentioned in connection with step a of the process of formula (3) above can be used in substantially the same manner as described in that step.
With respect to the solvent, reduction catalyst, acylating agent, reaction conditions (e.g., reaction temperature and reaction pressure) and the like to be employed in the reaction of formula (9), those which are mentioned in connection with step a of the process of formula (3) above can also be employed.
The WAnQ(6xe2x88x92n) obtained by the reaction of formula (9) can be isolated by a conventional method. For example, the isolation can be conducted by a method comprising: removing the catalyst from the reaction mixture by filtration to obtain a filtrate; and distilling off the solvent from the filtrate (see, for example, Example 6).
The WAnQ(6xe2x88x92n) can also be obtained by subjecting a WB6 to reductive dearylmethylation in the presence of an acylating agent, as shown in the following formula (10): 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, each Q independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms provided that all of Q""s are not simultaneoulsy hydrogen atoms, and W represents a hexavalent hexaazaisowurtzitane residue.
With respect to the solvent, reduction catalyst, acylating agent, reaction conditions and the like to be employed in the reaction of formula (10), those which are mentioned in connection with step a of the process of formula (3) above can be employed.
The isolation of the obtained WAnQ(6xe2x88x92n) can be conducted by the method mentioned in connection with the reaction of formula (9) above.
In the WB6 and WAnB(6xe2x88x92n) (wherein n is 4 or 5), each of which can be used as a starting material for synthesizing the acyl group-containing hexaazaisowurtzitane derivative of the present invention, the arylmethyl group represented by B is an aryl group-substituted methyl group, and generally has 7 to 21 carbon atoms. A representative structure of the arylmethyl group B is represented by the following formula (XIII):
xe2x80x94CH2Arxe2x80x83xe2x80x83(XIII)
wherein Ar represents an aromatic group having 6 to 20 carbon atoms.
The number of carbon atoms of the Ar in formula (XIII) above is generally in the range of from 6 to 20, preferably from 6 to 10, most preferably 6. Examples of Ar""s include a phenyl group; alkylphenyl groups, such as a tolyl group (o-, m- and p-isomers), an ethylphenyl group (o-, m- and p-isomers), and a xylyl group; alkoxyphenyl groups, such as a methoxyphenyl group (o-, m- and p-isomers), an ethoxyphenyl group (o-, m- and p-isomers), and a butoxyphenyl group (o-, m- and p-isomers); and unsubstituted and substituted naphthyl groups. Of these, a phenyl group and alkoxy phenyl groups are preferred. In each of the WB6 and WAnB(6xe2x88x92n) (wherein n is 4 or 5), the arylmethyl groups may be the same or different.
The acyl group-containing hexaazaisowurtzitane derivative of the present invention represented by formula (I) WAtQ(6xe2x88x92t) (wherein t is an integer of from 4 to 6) can be synthesized by various methods as described above.
The most characteristic feature of the methods for producing the acyl group-containing hexaazaisowurtzitane derivative of the present invention represented by formula (I) resides in that a reductive dearylmethylation reaction of a WB6 is conducted in the presence of an acylating agent.
This reaction is represented by the following formula (11): 
wherein p represents an integer of from 1 to 5, t represents an integer of from 4 to 6, B represents an arylmethyl group, A represents an acyl group having 1 to 10 carbon atoms, each Q independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and W represents a hexavalent hexaazaisowurtzitane residue.
The molar ratio of the WApB(6xe2x88x92p) to the WAtQ(6xe2x88x92t) in the reaction mixture obtained by the reaction of formula (11) above is generally in the range of from 0.001 to 1,000, preferably from 0.01 to 100.
With respect to the solvent, reduction catalyst, acylating agent, reaction conditions and the like to be employed in the reaction of formula (11), those which are mentioned in connection with the reaction of formula (8) above can be employed.
In conducting the production of the acyl group-containing hexaazaisowurtzitane derivative of the present invention represented by formula (I-a) by subjecting WB6 to reductive dearylmethylation in the presence of an acylating agent, it is important that a) formation of an Nxe2x80x94H group by the reductive elimination of the arylmethyl group B, and b) formation of an N-acyl group by the acylation of the Nxe2x80x94H group, are successively effected.
The above-mentioned formula (11) indicates that not only is WApB(6xe2x88x92p) (wherein p represents an integer of from 1 to 5) produced from WB6, but also WAnH(6xe2x88x92n) is produced by a further reaction of the WApB(6xe2x88x92p).
In the reaction of formula (11), the reductive dearylmethylation reaction is terminated when a reaction mixture [comprising WApB(6xe2x88x92p) and WAtQ(6xe2x88x92t)] having a desired composition has been obtained. Specifically, the advance of the dearylmethylation reaction is monitored by gas chromatography or liquid chromatography, and the reaction is terminated when a reaction mixture having a desired composition has been obtained.
Hereinbelow, an explanation is first given with respect to a presumed route of the reaction of formula (11), and then an explanation is given with respect to the utility and use of the reaction of formula (11).
The presumed route of the reaction of formula (11) is described in detail in the chart of the following formula (12). Since an N-alkyl group may be formed by the reduction (as a side reaction) of an N-acyl group, which reduction may occur depending on the reaction conditions, a by-produced, N-alkyl group-containing hexaazaisowurtzitane derivative is also described in the chart of formula (12). In the chart of formula (12), A represents an acyl group having 1 to 10 carbon atoms, B represents an arylmethyl group, R represents an alkyl group having 1 to 10 carbon atoms, H represents a hydrogen atom, and W represents a hexavalent hexaazaisowurtzitane residue. 
When the reaction of formula (11) is conducted in a batchwise manner, the proportions of reaction products obtained vary depending on the reaction time. When the reaction of formula (11) is conducted in a continuous manner, the proportions of reaction products obtained vary depending on the contact time. Further, the proportions of reaction products obtained may also vary depending on the types of the catalyst and solvent employed, the reaction temperature and the like. Therefore, in the reaction of formula (11), the proportions of reaction products can be varied in a desired ratio by appropriately selecting the reaction conditions.
The utility of the reaction of formula (11) is described below in detail.
When it is attempted to obtain the acyl group-containing hexaazaisowurtzitane derivative of the present invention from WB6 by first subjecting WB6 to reductive dearylmethylation in the absence of an acylating agent to obtain WHnB(6xe2x88x92n) (wherein n represents an integer of from 1 to 6) and subsequently acylating the obtained WHnB(6xe2x88x92n), the desired product cannot be obtained in high yield due to a decomposition of the W skeleton. The reason for this is presumed to reside in that secondary amino group-containing hexaazaisowurtzitane derivatives (such as WHB5, WH2B4 and WH3B3) formed by the reductive dearylmethylation of WB6 in the absence of an acylating agent are structurally unstable. By contrast, by the method of the present invention using the reaction of formula (11) in which the reductive dearylmethylation of WB6 is conducted in the presence of an acylating agent, an acyl group-containing hexaazaisowurtzitane derivative can be synthesized without occurrence of the decomposition of the W skeleton. The reason for this is believed to reside in that, in the reaction of formula (11), unstable, secondary amino group-containing hexaazaisowurtzitane derivatives (such as WHB5 and WH2B4) (which are produced in the early stage of the reaction) are immediately acylated and thus stabilized in the reaction system, so that the decomposition of the W skeleton can be suppressed, thereby allowing the dearylmethylation and acylation to further proceed.
As described above, the acyl group-containing hexaazaisowurtzitane derivative of the present invention represented by formula (I-a) can be synthesized in a single step by subjecting WB6 to reductive dearylmethylation in the presence of an acylating agent. However, when it is attempted to complete the reaction in a single step, a wide variety of reaction products are formed at once and side reactions markedly occur. The present inventors have made studies to develop a method which can solve these problems and can produce WAtH(6xe2x88x92t) (wherein t represents an integer of from 4 to 6) advantageously on a commercial scale and with high selectivity and in high yield. As a result, it has been found that, by conducting the above-mentioned reactions of formulae (8), (6) and (1) in this order, very good results can be obtained.
The following is a more detailed explanation of each of the reactions of formulae (8), (6) and (1).
I. The Reaction of Formula (8):
For producing WAnB(6xe2x88x92n) in high yield in the above-mentioned reaction of formula (8), there can be employed various methods. Examples of such methods include:
1) a method in which the types and amounts of the reaction reagents are selected so that the reductive dearylmethylation reaction can terminate before completion;
2) a method in which the advance of the reductive dearylmethylation reaction is monitored by gas chromatography or liquid chromatography, and the reaction is terminated at an appropriate point in time; and
3) a method in which a solvent which is a good solvent for WB6 but a poor solvent for WAnB(6xe2x88x92n) (e.g., an aromatic compound, such as ethylbenzene or toluene) is used so as to cause WAnB(6xe2x88x92n) produced by the reductive dearylmethylation of WB6 to be precipitated from the reaction mixture.
Of methods 1), 2) and 3) above, method 3) is commercially most advantageous from the viewpoint of ease in operation.
In the reaction of formula (8), for suppressing side reactions to improve the selectivity for WAnB(6xe2x88x92n), it is advantageous to use as an acylating agent a carboxylic ester of N-hydroxysuccinimide, such as N-acetoxysuccinimide, or a mixture of a carboxylic ester of N-hydroxysuccinimide and a carboxylic anhydride, such as acetic anhydride. When such an acylating agent is used, not only the selectivity for WAnB(6xe2x88x92n) but also the yield of WAnB(6xe2x88x92n) can be improved. The reason why the selectivity for WAnB(6xe2x88x92n) is improved when a carboxylic ester of N-hydroxysuccinimide is used as an acylating agent has not yet been elucidated. However, it is believed that such a difference in the selectivity for WAnB(6xe2x88x92n) between a carboxylic ester of N-hydroxysuccinimide and other acylating agents, such as a carboxylic anhydride, is ascribed to the difference in not only reactivity but also substrate specificity due to the steric restrictions (including specific three-dimensional structure and bulkiness) of the acylating agent.
The above fact that, when a carboxylic ester of N-hydroxysuccinimide is used as an acylating agent, the selectivity for WAnB(6xe2x88x92n) can be remarkably improved has for the first time been found by the present inventors. This finding is very important for synthesizing WAnB(6xe2x88x92n) with commercial advantages.
II. The Reaction of Formula (6):
When the reductive dearylmethylation of WAnB(6xe2x88x92n) produced in the reaction of formula (8) is conducted in the presence of an acylating agent to synthesize WA6, side reactions, such as formation of N-alkyl due to the reduction of N-acyl, are likely to occur, so that it becomes difficult to synthesize WA6 with high selectivity.
By contrast, when the reductive dearylmethylation of WAnB(6xe2x88x92n) is conducted in the absence of an acylating agent as shown by the reaction of formula (6), side reactions, such as formation of N-alkyl group, are suppressed, so that the reductive dearylmethylation reaction proceeds with high selectivity. This phenomenon has been found by the present inventors. From a reaction mixture obtained by the reductive dearylmethylation reaction of formula (6), high purity WAnH(6xe2x88x92n) can be obtained in high yield by a simple isolation operation. Therefore, this reaction of formula (6) is very useful for synthesizing WAnH(6xe2x88x92n).
As mentioned above, when the reductive dearylmethylation reaction of WB6 is conducted in the absence of an acylating agent, the produced WHnB(6xe2x88x92n) (wherein n represents an integer of from 1 to 6) is unstable in the reaction system, so that it is difficult to obtain WHnB(6xe2x88x92n) in high yield. By contrast, as mentioned above, WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) is stable in the reaction system, so that WAnH(6xe2x88x92n) can be synthesized in high yield.
The reason why WHnB(6xe2x88x92n) (wherein n represents an integer of from 1 to 6) and WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) have different properties from each other, has not yet been elucidated. However, it is believed that a difference in properties between arylmethyl group B and acyl group A produces the difference in stability between the respective hexaazaisowurtzitane skeletons of WHnB(6xe2x88x92n) and WAnH(6xe2x88x92n).
The above-mentioned difference in properties between WHnB(6xe2x88x92n) (wherein n represents an integer of from 1 to 6) and WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) has for the first time been found by the present inventors. Further, the hexaazaisowurtzitane compound represented by the formula WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) is not disclosed in any literature, and has for the first time been synthesized by the method of the present invention.
III. The Reaction of Formula (1):
As mentioned above under xe2x80x9cprior artxe2x80x9d herein, WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) as such can be advantageously used as various functional materials, such as a precursor of a polynitrohexaazaisowurtzitane derivative and a material for a highly polar polymer. If desired, WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) can be easily converted to WA6 by effecting the reaction of formula (1).
WA6 is not disclosed in any literature, and has for the first time been synthesized by the present inventors. WA6 can also be advantageously used as various functional materials, as in the case of WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5).
The acyl group-containing hexaazaisowurtzitane derivative of the present invention represented by the formula (I-a) WAtH(6xe2x88x92t) (wherein t represents an integer of from 4 to 6) can be used as a starting material in the nitration reaction to thereby obtain a polynitrohexaazaisowurtzitane derivative.
The following explanation provides an example of methods for subjecting WAtH(6xe2x88x92t) (n represents an integer of from 4 to 6) of the present invention to a nitration reaction for converting an Nxe2x80x94H group and Nxe2x80x94A group thereof to Nxe2x80x94NO2 groups.
An Nxe2x80x94H group of the WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) of the present invention can be converted to an Nxe2x80x94NO2 group by various nitration methods. For example, WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) can be easily converted to WAn(NO2)(6xe2x88x92n) (wherein n represents an integer of from 4 to 5) in a single step. However, from the viewpoint of improving the yield of the desired WAn(NO2)(6xe2x88x92n), it is preferred to conduct the conversion of an Nxe2x80x94H group to an Nxe2x80x94NO2 group by a method comprising two steps as shown in the reaction formula (13) below.
Illustratively, as shown in reaction formula (13) below, an Nxe2x80x94H group of WAnH(6xe2x88x92n) is nitrosated to an Nxe2x80x94NO group, and the Nxe2x80x94NO group is nitrated to an Nxe2x80x94NO2 group to thereby obtain WAn(NO2)(6xe2x88x92n). 
wherein n represents an integer of from 4 to 5, A represents an acyl group having 1 to 10 carbon atoms, H represents a hydrogen atom, (NO) represents a nitroso group, (NO2) represents a nitro group, and W represents a hexavalent hexaazaisowurtzitane residue.
As a nitrosating agent used in the process of formula (13), any nitrosating agent can be employed as long as it is capable of nitrosating WAnH(6xe2x88x92n) to produce WAn(NO)(6xe2x88x92n). Generally, a mixture of sodium nitrite and an acid; dinitrogen tetraoxide; nitrosyl chloride and the like are used as nitrosating agents.
The nitrosation reaction temperature is generally in the range of from xe2x88x9250xc2x0 C. to 200xc2x0 C., preferably from xe2x88x9230xc2x0 C. to 100xc2x0 C., more preferably from xe2x88x9220xc2x0 C. to 50xc2x0 C.
As an oxidizing agent used in the nitration reaction in the process of formula (13), any oxidizing agent can be employed as long as it is capable of oxidizing a nitroso group to produce a nitro group. Generally, examples of oxidizing agents include nitric acid and hydrogen peroxide. Of these, nitric acid is preferred. These oxidizing agents can be used individually or in combination.
The oxidation reaction temperature is generally in the range of from xe2x88x9250xc2x0 C. to 200xc2x0 C., preferably from xe2x88x9230xc2x0 C. to 150xc2x0 C., more preferably from xe2x88x9220xc2x0 C. to 60xc2x0 C.
Also, an Nxe2x80x94A group of the WAtH(6xe2x88x92t) (wherein t represents an integer of from 4 to 6) of the present invention can be easily converted to an Nxe2x80x94NO2 group by nitration with nitric acid or a mixture of nitric acid and dinitrogen pentoxide as apparent from, for example, Example 21 (infra). For example, WA6 can be converted to a polynitrohexaazaisowurtzitane derivative, such as WA4(NO2)2, by various nitration methods, for example, using a mixture of nitric acid and dinitrogen pentoxide as a nitrating agent.
Further, as shown in the reaction formula (14) below, various hexaazaisowurtzitane derivatives represented by the formula WAnE(6xe2x88x92n) can be nitrated to thereby obtain hexanitrohexaazaisowurtzitane [W(NO2)6]. 
wherein n represents an integer of from 4 to 6, A represents an acyl group having 1 to 10 carbon atoms, E represents a nitroso group or a nitro group, and W represents a hexavalent hexaazaisowurtzitane residue.
As a nitrating agent to be used in converting an Nxe2x80x94A group of WAnE(6xe2x88x92n) to an Nxe2x80x94NO2 group, any nitrating agent can be employed as long as it is capable of converting an Nxe2x80x94A group to an Nxe2x80x94NO2 group. For example, various nitrating agents containing nitric acid can be used. Illustrative examples of nitrating agents include nitrating agents containing a strong protonic acid, such as nitric acid/sulfuric acid nitrating agents or nitric acid/trifluoroacetic acid nitrating agents.
The reaction temperature for the reaction of formula (14) is generally in the range of from xe2x88x9250xc2x0 C. to 120xc2x0 C., preferably from xe2x88x9220xc2x0 C. to 60xc2x0 C.
The reaction time for the reaction of formula (14) is generally in the range of from 0.1 to 500 hours, preferably from 1 to 200 hours.
As described hereinabove, the Nxe2x80x94H group and Nxe2x80x94A group of the W skeleton are functional groups which can be easily converted to nitro groups. Therefore, by using WAtH(6xe2x88x92t) (wherein t represents an integer of from 4 to 6) as an intermediate product, various polynitrohexaazaisowurtzitane derivatives can be produced in high yield.
As apparent from the above, according to the present invention, there is provided a method for producing a hexanitrohexaazaisowurtzitane represented by the following formula (IX):
i W(NO2)6xe2x80x83xe2x80x83(IX)
wherein NO2 represents a nitro group and W represents a hexavalent hexaazaisowurtzitane residue represented by the following formula (II): 
which comprises nitrating, with a nitrating agent, at least one compound selected from the group consisting of compounds which are, respectively, represented by the following formulae:
formula (III):
xe2x80x83WA6xe2x80x83xe2x80x83(III)
xe2x80x83wherein each A independently represents an acyl group having 1 to 10 carbon atoms, and W is as defined above,
formula (IV):
WAnH(6xe2x88x92n)xe2x80x83xe2x80x83(IV)
xe2x80x83wherein n represents an integer of from 4 to 5, H represents a hydrogen atom, and each of A and W is as defined above,
formula (VII):
WAn(NO)(6xe2x88x92n)xe2x80x83xe2x80x83(VII)
xe2x80x83wherein NO represents a nitroso group, and each of n, A and W is as defined above, and
formula (VIII):
WAn(NO2)(6xe2x88x92n)xe2x80x83xe2x80x83(VIII)
xe2x80x83wherein each of n, A, NO2 and W is as defined above.
The polynitrohexaazaisowurtzitane derivative prepared from the acyl group-containing hexaazaisowurtzitane derivative of the present invention can be advantageously used as an additive for modifying the properties of propellants and explosives, such as mechanical properties, detonation velocity, detonation pressure, burning rate, pressure exponent, sensitivity, heat resistance and the like, and also as a high performance material for explosives.
Described below are the advantages of the polynitrohexaazaisowurtzitane derivative prepared from the acyl group-containing hexaazaisowurtzitane derivative of the present invention.
For example, WA4(NO2)2 has the following advantageous properties:
1) WA4(NO2)2 has a similar molecular structure to that of a high performance explosive having a polynitramine group-containing cyclic structure, such as HNW, cyclotetramethylenetetranitramine (hereinafter referred to simply as xe2x80x9cHMXxe2x80x9d) and cyclotrimethylenetrinitramine (hereinafter referred to simply as xe2x80x9cRDXxe2x80x9d), and exhibits excellent heat resistance as compared to HNW, HMX and RDX. [Even when WA4(NO2)2 is used as an additive for propellants and explosives, there is no danger that it markedly lowers the heat resistance of the propellants and explosives.]
2) Differing from the above-mentioned nitramine compounds (i.e., HNW, HMX and RDX), WA4(NO2)2 has not only an N-nitro group but also an Nxe2x80x94A group in the skeleton thereof, so that it exhibits good affinity for a binder, such as polyurethane.
By adding the WA4(NO2)2 having the above-mentioned advantageous properties to propellants and explosives comprising a nitramine compound (such as HNW, HMX, RDX or the like) and a binder, such as polyurethane, the adhesion between the solid component (i.e. nitramine compound) and the binder can be improved.
The WA4(NO2)2 can be easily converted to HNW by nitration, so that it is useful as a raw material for producing HNW. HNW has a high density and high energy, so that it is very useful as an oxidizing agent for high performance explosives and smokeless propellants.
By reacting the tetraacylhexaazaisowurtzitane WA4H2 of the present invention with a dicarboxylic acid derivative, such as a dicarboxylic halide or dicarboxylic diester, a highly polar polymer having a hexaazaisowurtzitane skeleton in the main chain thereof can be obtained.
In synthesizing the acyl group-containing hexaazaisowurtzitane derivative WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 6) of the present invention, by using an acylating agent having a specific functional group, a crosslinkable polyacylhexaazaisowurtzitane can be obtained.
The WAnH(6xe2x88x92n) (wherein n represents an integer of from 4 to 6) of the present invention as such can also be used as additives, such as a polymer modifier.
Hereinbelow is given a flow chart showing preferred modes of the production methods involved in the present invention. 
As can be seen from the above flow chart, the acyl group-containing hexaazaisowurtzitane derivative WAtQ(6xe2x88x92t) (wherein W is a hexavalent hexaazaisowurtzitane residue, each Q is independently a hydrogen atom or a C1-C10 alkyl group and t is from 4 to 6) of the present invention can be produced from a hexakis(arylmethyl)hexaazaisowurtzitane WB6 (wherein W is as defined above and B is a C7-C21 arylmethyl group), directly or through an acyl group- and arylmethyl group-containing hexaazaisowurtzitane derivative WAnB(6xe2x88x92n) (wherein W and B are as defined above and n is 4 or 5) or WApB(6xe2x88x92p) (wherein W and B are as defined above and p is from 1 to 5). The acyl group-containing hexaazaisowurtzitane derivative WAtQ(6xe2x88x92t) (wherein W, A, Q and t are as defined above) can be easily converted to hexanitrohexaazaisowurtzitane W(NO2)6 (wherein W is as defined above) in high yield, directly or through a nitroso group-containing hexaazaisowurtzitane derivative WAn(NO)(6xe2x88x92n) (wherein W and A are as defined above and n is 4 or 5) and/or a nitro group-containing hexazaisowurtzitane derivative WAn(NO2)(6xe2x88x92n) (wherein W and A are as defined above and n is 4 or 5).